A method and device are disclosed for determining the distribution of the .beta. rays emerging from a surface. The device comprises an enclosure filled with a gas mixture having a first preamplification chamber between two grids, a second transfer chamber between two grids and a third multiplication chamber between two grids; as well as three DC voltage sources; and an impeding assembly.

A device according to the invention includes: a gas detector, comprising at least one chamber and containing a noble gas and a gas or vapor that emits photons between two parallel electrodes between which a continuous high voltage (HT) is applied, whereby a first electrode is intended for receiving, against its external face, the surface of the radioactive body to be observed; a brilliance amplifier arranged for receiving the photons emitted by the excited atoms which are produced in the vicinity of a second electrode by the electron avalanche ascribable to the electrical field between the first and second electrodes; a camera arranged behind the brilliance amplifier; and computing means capable of computing, from the output signal of the camera, the entrance points in said gas detector, at the first electrode, of the electrons emerging from said surface of the radioactive body.

A gas detector for ionizing radiation particularly of the .beta. type leading to the emission of energetic electrons by a surface adapted to provide for mono-dimensional or two-dimensional detection. The gas detector includes a sealed enclosure containing an ionizing electron generating gas and at least two grids at different electric potentials, one of them constituting the anode. One of the grids at least is formed in a first direction by a plurality of electrically insulating wires serving as a support and in a second direction, distinct from the first, by a plurality of electrically conductive and resistive wires which form a woven mesh.

A method for representing the spatial distribution of radioactive elements of radioactively labeled samples, by means of a screen of the erasable phosphor type, in which the labeled samples are placed near this screen in order to generate thereon a latent electronic image formed by the .beta. radiation or primary electrons generated by the radioactive elements. The primary electrons emitted by the radioelements are accelerated to an energy level lying between 20 keV and 1 MeV by means of an electric field E applied between the space separating the sample and the screen. The primary electrons subjected to acceleration in the space are confined, so as to limit the lateral excursion of these primary electrons. The latent image is formed, on this screen, from the confined and accelerated primary electrons. The primary electrons can generate low energy secondary electrons in CSI screens which are thus accelerated and focused to give enlarged images onto a screen.

A medical imaging device using X- or gamma ionizing radiation, provided with a source of radiation in a divergent beam diaphramed by a slit and a module for detecting a beam transmitted by a body to be observed, illuminated by the beam. The detection module comprises a drift chamber and a multiwire chamber which are filled with a gas, these chambers comprising, in a direction orthogonal to the plane containing the slit and the illumination beam, a drift space for the electrons, an electron proportional multiplier grid for generating multiplied electrons and corresponding ions and a second cathode electrode making it possible to count the multiplied electrons by means of the corresponding ions for a plurality of directions of the sheet-form illumination beam.

A device for forming images of ionizing particles through single-dimensional electrophoresis provided with a multi-wire proportional chamber. The chamber filled with a gas is of asymmetric structure and is formed successively by an entry window for the particles, taken to a negative potential, a multi-wire anode electrode, taken to a potential positive with respect to a reference potential, and a cathode electrode which is placed in the vicinity of the anode electrode. The cathode electrode, which is taken to the reference potential, is formed by a network of parallel electrically conducting strips. Detection of the position of impact of the ionizing particle along the pitch of the network is performed by induction of a delayed electric pulse caused by an avalanche of the ionization electrons issuing from the ionizing particle in the region of the strip situated in line with the impact by the particle in the chamber, the reference time being that of the ionization electrons close to the wires.

The invention relates to a medical imaging device using X or gamma ionizing radiation. It comprises a source (S) of radiation in a divergent beam, and a longitudinal slit (F) delivering a sheet-form beam in a plane containing the slit (F). A detection module is provided, which comprises a drift chamber and a multiwire chamber which are filled with a gas. The chambers comprise, in a direction orthogonal to the plane containing the slit (F), the drift space for the electrons, comprising a cathode electrode, a converter, a proportional multiplier anode for generating multiplied electrons and corresponding ions, and a second cathode electrode, placed in the vicinity of the multiplier anode. The multiplier anode and the second cathode electrode consist of conductor elements extending in two parallel planes, along substantially orthogonal directions, in order to permit two-dimensional localization of the electrons in this plane.

A high resolution radiographic imaging device for medical or industrial radiography includes at least one ionizing particles detector equipped with at least one gas chamber provided with a window for the lateral or frontal inlet of the illumination beam. A first, a second and a third flat electrode are placed in parallel with one another in order to form a conversion space and a amplification space with the distance separating the second and third electrodes being less than 200 .mu.m and the amplitude ratio of the electrical fields created between the second and third electrodes and the first and second electrodes being greater than 10.

This detector comprises a gas chamber containing plane electrodes delimiting conversion (C) and amplification (A) gaps. One of the electrodes is perforated with holes and forms the detector cathode. The distance between the detector cathode and the anode is less than 500 .mu.m. The intensity of the electric field in the amplification gap is ten times higher than the intensity of the electric field in the conversion gap. Application in particle physics, medicine, biology.